1. Field of the Invention
The present invention belongs to the group of friction type devices for connecting of hubs with shafts. The invention is applicable for connecting of a wide range of machine components for rotary motion transfer, such as shafts, wheels, gears, pulleys, Couplings, bearings, and so forth.
2. Description of the Related Art
Machine components for transferring rotary motion, such as shafts, wheels, gears, pulleys, couplings, and so forth, are the basic elements of virtually every machine. A reliable connection of an external cylindrical surface of a machine component (e.g., a shaft) with an internal cylindrical surface of another machine component (e.g., a bore of a hub) is essential for proper functioning and servicing of the machinery.
A removable and reusable shaft/hub connection device should fulfill three basic functions. First, the device should reliably secure the desired position of the connected components. Second, the device must be able to transfer forces from one element to the other. Third, the device should permit easy assembly and disassembly of the components.
Friction type shaft/hub connecting devices function by creating pressure (normal forces) between the bore of the hub and the shaft, which results in a friction force. The generated friction force is proportional to the applied pressure and the friction coefficient between the surfaces in contact. There are a number of ways to create contact pressure between the hub and shaft. A commonly used method is to utilize the wedging action of an inner and an outer cone. An inner and an outer cone forced together in an axial direction generate a normal force between the surfaces in contact and cause an expansion of the outer cone and a compression of the inner cone. The magnitude of the normal force is directly proportional to the applied axial force and inversely proportional with the sinus of the wedge angle.
The simplest arrangement to utilize this wedging action for a shaft/hub connection is to shape the shaft and the bore of the hub as a cone. This frequently used method has the disadvantage that the hub and the shaft must have precisely machined matching conical surfaces. The standard requirement is generally to connect a cylindrical hub with a cylindrical shaft.
A number of conical shaft/hub locking devices have been previously developed to lock cylindrical shafts and hubs. There are two principle types of arrangements of these devices, which will be referred to as external and internal types. The external type has an external cone arrangement that clamps a thin wall extension of the hub by elastically deforming and compressing the hub to the shaft. The internal types are inserted into the bore of the hub bridging the gap between the shaft and bore and clamping by a wedging action of the inserted conical arrangement.
Many of the existing conical shaft/hub locking devices, such as the popular conical shrink disks or conical compression rings, do not provide sufficient support and accurate positioning. Additional measures, such as cylindrical centering surfaces or centering inserts manufactured to tight tolerances, are needed in these devices to avoid an excessive radial and axial runout of the connected components. Moreover, a long supporting base is usually required next to the centering surfaces to provide a strong and rigid support for the component (i.e., the gear, wheel, etc.) on the shaft.
There are a number of conical shaft hub locking devices having a spiral, thread type arrangement of grooves to make an assembly possible. Such locking devices are disclosed, for example, in U.S. Pat. Nos. 2,434,152, 2,819,090, 4,407,603, 4,464,140, 4,461,592, 4,460,289, and 5,044,817, and European Patent Publication No. EP 0 377 492 B1. The grooves of these patented devices comprise threads with a triangular thread profile. The assembly and disassembly process consists of screwing the inner bushing into the outer bushing.